The present invention relates to belt tracking systems, especially for use in screen printing conveyor driers. Such driers comprise a web of heat resistant screen material mounted over drive and idler rollers which conveys freshly printed matter through a drying oven. The problem is, the web of material which comprises the conveyor belt tends to wander towards one side or the other of the machine.
To solve this, some artisans use a crown roller, tending to create increased pressure on the center of the belt or web and thereby keep it on track. The problem with this approach is that it causes the belt to wear excessively in the center. This is particularly true in driers since the belt comprises a web of net-like material rather than a solid material.
Another attempt to solve this problem has been to provide a thrower roller adjacent either the idler or drive roller. If the conveyor belt is shifting one way, one positions the thrower roller so that it tends to throw the belt the opposite way. The problem with this approach is that constant attention to the belt position and constant readjustment of the thrower roller are both required. This results in part from the fact that the heat of the drier oven tends to cause changes in the configuration of the machine and/or the belt. Further, the belt material itself, being net-like and hence somewhat flimsy tends to change configuration as it is used.
Consequently, prior artisans have had considerable difficulty in keeping a conveyor belt, particularly in an environment such as a screen printing drier, tracking on a fixed path. Attempts to solve this problem have not met with great success.